Understanding Tsunamis

A tsunami is a wave (or series or waves) in the ocean that can be hundreds of miles long and have been known to reach heights of up to 34 feet. These waves can travel extremely fast...the tsunami of December 2004 traveled at about 300 miles per hour.

Tsunamis are usually caused by underwater earthquakes. When part of the sea floor snaps upward, energy from that sudden upward force causes the water to rise, forming the tsunami's wave(s). These waves travel in the form of an outward-moving ripples. When part of the wave approaches a rising slope in the sea floor (usually as it approaches land) the wave will rise, giving it additional height. When a tsunami finally reaches land, the area of greatest risk is within 1 mile of the shoreline.

Surviving a Tsunami

If you live near a shoreline and feel an earthquake, you should alert your family and go as far inland as possible(seek higher ground). Depending on the strength of the earthquake and it's location, you may have only a matter of minutes to evacuate yourself and your family.

If you are on the beach and you notice the ocean receding much further than normal, a tsunami could be imminent. Go as far inland as possible and seek higher ground.

The debris that the waves carry inland is just as destructive as the waves themselves. Also, tsunamis can consist of several waves instead of the one massive wave that most people think of. The force of each successive wave pushes water further inland causing severe flooding up to 1 mile from the shoreline. The spread of flood waters will depend on the strength of the tsunami as well as the geography of the affected land. Flatter land is more easily flooded than land that slopes above sea level.

All photos courtesy of USGS